The fundamental unit of crystalline silicate structures is a tetrahedral complex consisting of the Si cation in a tetrahedral coordination with four oxygens. In some structures, the tetrahedra link to form chains which result in fibrous or needlelike morphologies. Single chains result when SiO.sub.4 tetrahedra are joined at two oxygen atoms.
In other silicate structures, the tetrahedra are linked in layers or sheets as in mica minerals. Similar arrangement of the tetrahedra are found in clay minerals wherein two types of sheets may exist, one consisting of aluminum, iron or magnesium ions in a six-fold coordination with oxygens. The layer or sheet structures result from linking between three corners of each tetrahedron to neighboring tetrahedra. Breck, Zeolite Molecular Sieves, John Wiley & Sons, A Wiley Interscience, Publication New York, London, Sydney, Toronto, p. 31 (1974) reports that these layer or sheet structures do not have three-dimensional stability and may expand if the layers are forced apart by water, other molecules or ions, and thus, differ from silicates referred to as zeolites.
If the SiO.sub.4 tetrahedra are linked in three dimensions by a mutual sharing of all of the oxygen atoms, a framework structure results. The family of zeolites embraces this characteristic and is characterized by the resulting three dimensional framework structure. One such zeolite is ZSM-12. That zeolite ZSM-12, its preparation and its distinctive X-ray diffraction pattern which identifies it and distinguishes it from other known crystalline silicates are taught by U.S. Pat. No. 3,832,449, the entire disclosure of which is incorporated herein by reference. U.S. Pat. No. 4,482,531, which is incorporated by reference herein in its entirety, describes the preparation of ZSM-12 from a reaction mixture containing sources of oxides of certain inorganics and containing adducts of diazabicyclo[2.2.2]octane and an .alpha.,.omega.-dihaloalkane.